Conventionally, hybrid vehicles including an engine and an electric rotating machine as power sources are known. Further, in this type of hybrid vehicles, there are also known hybrid vehicles provided with a power dividing mechanism capable of distributing input power at a predetermined distribution ratio and outputting the distributed input power.
For example, Patent Literature 1 described below discloses a drive system of a hybrid vehicle provided with a power dividing mechanism for distributing power of an engine to a first motor/generator and to drive wheel sides at a predetermined distribution ratio. The drive system employs a planetary conical mechanism including a carrier coupled with an engine, a sun gear coupled with a first motor/generator, a ring unit coupled with the drive wheel sides, and a pinion unit having a conical abutment surface as the power dividing mechanism. The drive system operates the engine on an optimum fuel consumption line by changing the distribution ratio at a predetermined vehicle speed or more.
Further, Patent Literature 2 described below discloses a drive system of a hybrid vehicle provided with a power dividing mechanism (power distribution device) having a first rotating element coupled with a first motor/generator, a second rotating element coupled with an engine, a third rotating element coupled with an output member, a fourth rotating element, and a switch mechanism for coupling or releasing a second motor/generator with or from the second rotating element or the fourth rotating element. When a transmission ratio (ratio between an engine rotation number and a rotation number of the output member) of the power dividing mechanism is reduced, the drive system couples the second motor/generator with the second rotating element, regeneratively controls the second motor/generator by transmitting a part of power of the engine to the second motor/generator, and supplies generated electric power to the first motor/generator. With the operation, the drive system avoids a so-called power circulation phenomenon in which power of the first motor/generator is converted to electric power by the second motor/generator, and the electric power is supplied to the first motor/generator and converted to power again.
Incidentally, Patent Literature 3 described below discloses a continuously variable transmission provided with a continuously variable transmission mechanism, which has balls (rolling members) clamped between an input disc and an output disc and changes a transmission ratio by adjusting a tilt angle of the balls, and a planetary gear mechanism (differential mechanism) whose one of rotating elements is coupled with an output shaft of the continuously variable transmission mechanism. Specifically, Patent Literature 1 describes the planetary gear mechanism in which a sun gear as one of the rotating elements is coupled with its output shaft, a carrier is coupled with drive wheel sides, and a ring gear is coupled with an output side of a drive power source via a group of gears.